Emotional contagion—emotions being linked across people—has captured psychologists’ attention yet little is known about its
mechanisms. Early influential treatments focused on primitive mimicry. Later accounts emphasized (a) social comparison, whereby
people compare their feelings with compatriots’, (b) emotional interpretation, where others’ expressive displays serve as
information, and (c) empathy, or imagining another person’s feelings. This paper introduces affective process theory (APT), which unifies these mechanisms and identifies others. Using a rule-governed theoretical process, APT reveals 10 distinct
mechanisms that connect people’s affective states, which fall into three types. Convergent linkage occurs when individuals share the same vantage point and interpretations of emotionally evocative stimuli. Divergent linkage occurs with a shared vantage point but different interpretations. Complementary linkage occurs when the other person is itself the stimulus. APT integrates past findings on moderating factors such as social closeness
and cooperation. Implications for practice and future research are discussed.